Automatic systems for shutting down internal combustion engines have typically responded when the engine's operating temperature exceeds safe engine performance limits. U.S. Pat. No. 4,074,672, "Shutoff Apparatus for Internal Combustion Engines", discolses such a shutdown system.
Shutdown systems are intended to be safety devices to protect their guarded engines. Some shutdown devices, however, create additional safety concerns by switching operating circuitry to ground. This action creates current surges and high circuit temperatures which may damage circuit elements.
The shutdown circuit in U.S. Pat. No. 4,074,672, is designed for use with ignition systems for spark-fired internal combustion engines. The circuit uses a sensor to detect when the engine is overheating. An overheated engine status switches the sensor and completes a path to ground for current normally flowing to the ignition coil for the engine. The grounded ignition coil no longer produces the needed voltage to fire the engine's spark plugs. The engine, therefore, shuts off.
The grounding circuit in U.S. Pat. No. 4,074,672, has the potential of creating current surges and high temperatures. These conditions may damage such components as an induction coil in an ignition system, solenoids in fuel valves for diesel engines, or windings on electrical motors. High temperatures during switching could also ignite flammable materials in the circuit's environment causing personal injury and equipment damage.
The above deficiencies in a grounding engine shutdown system are overcome by the invention. Instead of grounding ignition system components, the invention disconnects the circuit which energizes a power generating device. This act produces no excessive current or heat surges in the circuit.
The invention's operation may be generally applied to power generating and power transmitting devices. The invention senses a potentially device damaging condition, switches open the circuit energizing that power generating or power transmitting device, and safely turns off the device. Additionally, the invention provides diagnostic feedback to an operator to identify why the power generating or power transmitting device was automatically turned off.